With an advent of third generation wireless networks, a number of multi-mode mobile devices simultaneously compatible with different network access technologies have entered the marketplace. Typical multi-mode devices are capable of accessing one or more cellular based network access technologies, as well as Wi-Fi based networks that offer reduced mobility but increased throughput within the coverage area. Such devices extend the consumer's ability to access Internet Protocol (IP) based applications that typically require availability of high speed network access in order to satisfy their inherent Quality of Service (QoS) requirements. For example, streaming video and Voice-over-IP (VoIP) applications have strict QoS constraints that necessitate availability of high bandwidth/low latency environments, especially in the face of inherent mobility of wireless users. A typical multi-mode mobile device may be programmed to select a high throughput Wi-Fi network when available and a cellular network when the Wi-Fi connection is not available.
In next generation wireless access networks, the radio network is connected to an access gateway, which serves a mobile device. The access gateway performs the mobility agent function to support the network layer mobility of the mobile device. The handoff of the mobile device is typically triggered by its mobility across serving areas of different access gateways associated with access networks based on either identical or diverse network access technologies. To preserve the user experience across a variety of access networks, the IP multimedia service session must be maintained under mobile conditions, which may necessitate a handoff of the service session between access networks, including a handoff between access networks based on heterogeneous technologies. However, typical handoff schemes between wireless access networks do not take into account the QoS constraints associated with ongoing IP service sessions. The absence of a handoff scheme that preserves the negotiated service-level QoS constraints has an adverse effect on the end-user experience and efficiency of utilization of network resources.